The free-living amoeba, Naegleria fowleri, is the causative agent of primary amebic meningoencephalitis, a rare but rapidly fatal central nervous system disease of man.N. fowleri has been isolated from thermally elevated aquatic environments worldwide, but the environmental conditions that "elect for virulent strains which become pathogenic in man are incompletely understood. A newly operational nuclear power plant (Clinton Nuclear Reactor) provides an opportunity to perform a longitudinal before and after study of the impact of thermal enrichment and elevated water temperatures on the thermal biology of N. fowleri. I propose to evaluate the following hypothesis: thermal enrichment from a nuclear reactor cooling system will elevate the water temperature of Clinton Lake, causing selection or amplification of thermophilic strains of the free-living , pathogenic amoeba, Naegleria fowleri. Specific aims of this study are to isolate and identify thermophilic strains of Naegleria spp. The "V" shaped lake will be divided into two study areas: east arm (heat sink) receiving heated water and west arm (unheated). Water and sediment samples will be collected from both arms of the lake for comparative study. Water samples will be filtered and amoebae isolated, identified by morphology, in-vitro cultivation, temperature tolerance, serology, enzyme activity profiles, and newly developed methods of DNA fingerprinting. Amoeba strains will be tested for pathogenicity by intranasal infection of laboratory mice. Environmental water quality parameters will be monitored to identify abiotic factors influencing the possible induction of thermophilic strains of amoebae. Statistical correlations will be made between water quality parameters and occurrence of amoebae.